Electrostatic printer

ABSTRACT

A stream of ink drops is electrostatically moved in a printing course from each of a plurality of supply nozzles toward an ink receiving carrier which is moved vertically in a straight path transversely of said course. A sweep voltage associated with each nozzle is repeatedly generated across a first pair of parallel electrodes which are generally horizontally spaced laterally of said course, and has a magnitude adapted for deflecting the associated stream generally horizontally in repeated lines extending transversely of the path of carrier travel and the course between the nozzle and the carrier. The movement of the carrier is adapted to generate one dimension of a two dimensional character from each stream, the sweep of the trace made by the associated &#39;&#39;&#39;&#39;horizontally&#39;&#39;&#39;&#39; deflected ink stream generating the other dimension. A print or nonprint mode is produced by selected of a pair of voltages applied across a second pair of parallel electrodes which are disposed about the course of each stream and generally vertically spaced. In the print mode, each stream remains in its printing course by clearing the edge of a mask. In the nonprint mode, each stream is deflected generally vertically from its course onto the mask and prevents printing. Accordingly, character definition is obtained. The edge of the mask is a sawtooth configuration having sloping segments, each of which is associated with one stream. To produce characters which are &#39;&#39;&#39;&#39;squared&#39;&#39;&#39;&#39; to the carrier, the electrodes of each first pair are nonparallel to the direction of the path of carrier movement. Their angle of tilt from a parallel condition is a function of the speed of the carrier such that a line trace resulting from a single sweep of an associated stream of ink drops will mark the carrier normal to the path of carrier movement; and the edge of the mask is parallel to the line along which each ink stream is &#39;&#39;&#39;&#39;horizontally&#39;&#39;&#39;&#39; deflected when printing.

United States Patent Metz [54] ELECTROSTATIC PRINTER Jack L. Metz, DesPlaines, Ill.

[73] Assignee: Teletype Corporation, Skokie, Ill. 22 Filed: J1me10,1970,

[21] Appl.No.: 44,953 i I [72] Inventor:

[52] US. CL.

3,409,904 11/1968 Maiershofer. .346/ 101 3,484,794 12/1969 Winston..346/75 3 ,488,664 l/l970 Winston.... ..346/ 75 3,500,436 3/1970 Nordin....346/75 -3 ,5 1 2,158 5/1970 Scarbrough ..346/76 OTHER PUBLICATIONGamblin et al: Orthogonalization of electrostatic printing:

IBM technical Disclosure Bulletin, Vol. 11, No. 10, March I969. pp1292-3 Primary Examiner-J0seph Wv Hartary Attomey-J. I... Landis and R.P. Miller [57] ABSTRACT A stream of ink drops is electrostatically movedin a printing course from each of a plurality of supply nozzles towardan ink [451 Feb. 8, 1972 receiving carrier which is moved vertically ina straight path transversely of said course. A sweep voltage associatedwith each nozzle is repeatedly generated across a first pair of parallelelectrodes which are generally horizontally spaced laterally of saidcourse, and has a magnitude adapted for deflecting the associated streamgenerally horizontally in repeated lines extending transversely of thepath of carrier travel and the course between the nozzle and thecarrier. The movement of the carrier is adapted to generate onedimension of a two dimensional character from each stream, the sweep ofthe trace made by the associated horizontally'- deflected ink streamgenerating the other dimension.

A print or nonprint mode is produced by selected of a pair of voltagesapplied across a second pair of parallel electrodes which are disposedabout the course of each stream and generally vertically spaced. 1n theprint mode, each stream remains in its printing course by clearing theedge of a mask. In the nonprint mode, each stream is deflected generallyvertically from its course onto the mask and prevents printing.Accordingly, character definition is obtained. The edge of the mask is'a sawtooth configuration having sloping segments, each of which isassociated with one stream.

To produce characters which are squared to the carrier, the electrodesof each first pair are nonparallel to the direction of the path ofcarrier movement. Their angle of tilt from a parallel condition is afunction of the speed of the carrier such that a line trace resultingfrom a single sweep of an associated stream of ink drops will mark thecarrier normal to the path of can'ier movement; and the edge of the maskis parallel to the line along which each ink stream is horizontallydeflected when printing.

3 Claims, 4 Drawing Figures PATENIEDFEBe I972 FIG.

2 mm T. m VL mK C A J FIG.

ATTORNEY ELECTROSTATIC PRINTER 4 FIELD OF THE INVENTION The presentinvention relates to printing. Particularly the invention relates toline raster printers. Specifically, the invention relates to anelectrostatic raster printer.

BACKGROUND OF THE INVENTION Raster printing is an art in which onedimension of a two dimensional character is generated by repeatedlyapplying an ink trace. on a carrier or ink receiving medium with inksweeping means. The other dimension of the character is generated byrelative movement of a succession of sweeps and the carrier in a pathtransversely of each sweep. Character definition is provided byselectively preventing ink deposition during selected sweeps.

Electrostatic printing, of one type, is an art in which a stream of inkdroplets is moved across a span-from a nozzle to a carrier on whichintelligence is printed. Character formation in said art is effectedthrough the agency of voltages which are generated about the inkdroplets in the span selectively to deflect the drops. y

In one form of the marriage of the aforesaid arts, which heretofor hasbeen consummated, the carrier moves continuously during printing.Accordingly, resulting characters are slanted; and that phenomenon isconsidered, in some circumstances, to be undesirable. Character slantingmay be obviated by printing while the carrier is stationary, withsuccessive line traces in each character rasterbeing advanced orstepped, one at a time, relative the stationary carrier and transverselyof each sweep until a character iscompleted. But, to follow the lastprocedure requires theaddition of electricalcomponents for advancingline traces which are not required'when the carrier moves continuouslyduring ink application.

It is an object of the present invention to provide an improved printingprocess and apparatus.

It is another object of the invention to provide an improved rasterprinting process and apparatus.

It is a further object of the invention to provide an improvedelectrostatic printing process and apparatus.

It is an additional object of the invention that the lines of a rasterand the direction of carrier movement are orthogonal in a rasterprinting art in which the character is continuously moving during theprinting.

It is yet a further'object of the invention to generate characterssquared to a continuously moving carrier in a raster printing art,particularly in which the recording material is an electrostaticallyimpelled stream of droplets.

SUMMARY OF THE INVENTION To effect the foregoing, and other objects ofthe invention which will become apparent from the ensuing description,one dimension of a two dimensional character is generated by moving acarrier in a path relative ink applying means in a raster printingprocess. The other character dimension is generated through a repeatedsweep force for applying successive linear ink traces transversely ofsaid path. Character definition is produced by preventing selected inkportions from being effective for printing. Means are provided forsloping each linear sweep at an angle other than perpendicular to thepath of carrier movement.

From another aspect, said objects are achieved in a printer of the typeadapted to generate one dimension of a two dimensional character bymoving a carrier on which ink is applied in a straight path. The otherdimension of the character is generated by means for directing the inkin repeated sweeps transversely of the straight path in response tochanging electrical effects. Means are provided for sloping each inksweep at an angle other than normal to the straight path. A mask havingan edge parallel to the sweeps and beyond which printing is effected isadapted to intercept selected portions of ink deflected from a coursetoward the carrier to provide character definition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is an elevational view of amodified embodiment of I the invention looking upstream through itselectrode assembly.

DETAILED DESCRIPTION OF THE INVENTION Referring now more particularly toFIG. 1 of the drawings, shown is a single printing assembly 10 whichincludes a reservoir 12 as a source for a recording material or ink. Thereservoir is fluidally connected through a conduit 14 to an electricallyconductive head 16 having ink applying means comprised of a deliverynozzle 18. In the illustrated embodiment, sufficient head pressure ismaintained for producing a meniscus from the downstream end of thenozzle to produce an intrusion of ink in a gap 20 generated by spacingan electrically conductive platen 22 downstream from and in printingalignment with the nozzle.

A carrier or ink receiving medium 24 is arranged to be moved in astraight path 25 at constant and uniform velocity over the upstream faceof platen 22 by motive means shown herein as a motor 26. To that endmotor output is coupled through a drive train, which may include apulley 28, to a sprocket wheel 30, the teeth of which are'proportionedfor feeding engagement in marginal apertures 32 of carrier 24. Path 25is considered vertical, as shown in the drawings relative which allterms of orientation in the specification is made.

Charging means which may be of conventional construction and of whichterminals 34 and 36 are shown respectively connectedto head 16 andplaten 22 provide a potential difference in gap 20, charge platen 22 andproduce an electrostatic charge on inkas it passes through head 16. Avalving electrode 38 is connected to a charge generator, only terminal40 of which is shown, and is disposed downstream of nozzle 18. It isadapted to generate an electrostatic field of sufficient magnitude todraw ink into a stream of drops 42 and initiate ink movement in a course41 toward carrier 24. The valving electrode has an aperture 39 which iscoaxially aligned with the bore of nozzle 18, and through which thestream will continuously flow under sufficient impelling force to reachthe carri- Parallel electrodes 43 and 44 of a first or vertical pairthereof are spaced downstream of valving electrode 38 and are generallyvertically spaced apart about course 41 permitting passage therebetweenof the stream of drops. Charging means of which only terminals 45 and 46are shown, are adapted for imposing selected of two voltage conditionsacross said last electrodes. In a first of the conditions, assembly 10is in an on or print mode and drops 42 are not affected. In the secondcondition, assembly 10 is in a nonprint or off mode -and the drops aredeflected vertically from course 41 to a course 48.

A mask 50 is disposed in intercepting or catching association with path48 downstream of electrodes 43 and 44 between platen 22 and parallelelectrodes 51 and 52 of a second or horizontal pair thereof. The lastmentioned electrodes are parallel to each other and are generallyhorizontally spaced apart, being disposed about path 41 downstream ofelectrodes 43 and 44.

A sweep generator 54 is connected to electrodes 51 and 52 through a pairof leads 55 and S6 for repeatedly deflecting drops 42 in a generallyhorizontal direction transversely of path 25 and course 41. By meanswhich may be known, the

value to a high value (FIG. 3), and after each voltage sweep to restoreitself for a repeat sweep. In consequence thereof, drops 42' which arepassing between the horizontal electrodes and are in course 41 (nothaving been deflected into course 48) will be moved from the left to theright in a manner such that a straight line of ink dots will be tracedor printed on carrier 24 transversely of the path 25 for each voltagesweep.

Accordingly, one dimension of any visual two dimensional design, such asan alphanumeric character, can be generated on carrier 24 by reason ofthe horizontal" sweep of the ink stream. The other dimension of suchdesign can be generated in consequence of movement of thecarrier. Theresult of the combinedeffect is a line raster. Character definition isadded by applying vertically deflecting voltages such that selecteddrops 42 from groups thereof which would be associated with selectedline traces, if printed, will be directed against mask 50. Control ofthe vertical electrodes through terminals 45 and 46 can be inaccordancewith programming which may be conventional.

A trough 58 is arranged in draining associationwith mask 50 and isadapted for collecting fluid which is directed is stream 48. Suitablemeans, such as a pump 60, which is fluidally connected to trough 58 isadapted to return ink caught on mask 50 to reservoir- 12. The foregoingconstruction precludes the requirement for shutting off ink flow fromnozzle 18 during the printing operation and thereby minimizes thelikelihood of nozzle cloggage which occasionally occurs in systems whichdo not maintain continuous flow from the nozzle during printing.

If, as in heretoforknown-devices, the direction of spacing of thehorizontal electrodes is normal to path 25, each line of a raster tracedon carrier 24 will slope in a manner such that the characters which areformed will not be squared to the carrier; and resulting printing willbe slanted. In accordance with the present invention, such result can beobviated. That is to say, the lines of each raster and path 25 can beorthogonal. To that end, the path of deflection of stream 41 during eachvoltage sweep is requiredto be at an angle to path 25 which is otherthan normal; the angle from normal through which the stream ishorizontally deflected being a function of carrier velocity.

Particularly, means for producing the result comprises electrodes 51 and52 disposed in a general lateral condition to the path 41; however,rotated (FIG. 2) slightly. about the axis of the bore of nozzle 18 suchthat the direction of spacing of said horizontal electrodes is at anangle other than normal to path 25. Said horizontalelectrodes whenthusly disposed are aptly and variously characterized as means forsloping the path along which ink 'is deposited on the carrier at anangle other than normal to the direction of the path of carriermovement, and means for sloping each sweep of the ink stream or each inktrace on carrier 24 at an angle other than perpendicular to thedirection of path 25.

Mask 50 has a straight edge 64 (FIG. 2) which is disposed adjacent path41 such that when a print mode is effected in assembly 10, drops 42 willclear or pass above edge 64 for impinging carrier 24. However, when anonprint mode is effected, the drops will be directed below said edge.According to another aspect of the invention, edge 64 extends parallelto the slope of the path taken by the drops during horizontaldeflection, means for deflecting selected portions of the drops againstsaid mask to prevent impingement on said carrier comprising electrodes43 and 44.

According to yet another aspect of the invention, the direction ofspacing of electrodes 43 and and the direction of spacing betweenelectrodes 51 and 52 are orthogonal. Accordingly, the direction of thespacing of electrodes 43 and 44 forms an angle with path 25 which isequal to the angle formed 7 by the direction of the spacing ofelectrodes 51 and 52 with the perpendicular to said path.

A modified embodiment of the invention has an assembly lltl (FIG. 4) forsimultaneously printing a plurality of designs or characters andcomprises a horizontal array 118 of nozzles.

each of which is similar to nozzle 18. The nozzles in the array aremounted in a framework 119 which also supports a plurality of electrodeassemblies 170 each of which is associated with a nozzle and disposedrelative thereto in the manner illustrated for the electrodes inassembly 10.

A unitary mask 150 is associated with and disposed downstream of all ofthe nozzles in the array. The mask has a window opening 151 with asaw-toothed edge comprised of a plurality of segments 164 each of whichcorresponds to a mask edge 64. Thatis to say, each segment 164 extendsparallel to the direction of horizontal" deflection or sweep of an inkstream of an associated nozzle when such stream is in a printing mode.By suitably selecting the number of nozzles in array 1l8 all of thehorizontal segments in a line of intelligence can be printedsimultaneously.

In the illustrated embodiment, each nozzle is adapted to provide astream for printing two alphanumeric characters at one time. That is tosay, assuming an on" print mode the stream issuing from one nozzle willbe swept from left to right with respect to FIG. 1, first to impinge thecarrier along segment I of row A continuing the sweep along segment IIof row A following a programmed interruption to enable proper characterspacing. Thereafter during an ensuing sweep and following rapid retraceduring which a nonprint mode is effected, a line would .betraced onsegment I of row B and thereafter, on'segment II of row B. Successiverows could be traced in -a like manneruntil a pair of characters willhave been completed, preventing ink from reaching selected areas of thecarrier by control of voltage across electrodes 43 and 44 An operatingembodiment of the illustrated apparatus is adapted to print characterseach of which has a matrix of 0.080 inch by l0.l0 0 inch with characterspacing 0.020 inch. Although two matrices-are shown traced in FIG. 1 forillustration, in practice they...are not traced on carrier 24. Onlydesired designs are traced, upper portions of two thereof being shown inFIG. 1. Each matrix has 80 dot positions for each character arranged in10 rows and eight columns, each dot position comprising a square adaptedfor reception of a plurality of drops 42, and each character matrixbeing spaced two columns from an adjacent thereof. Accordingly, eachadjoining horizontal pair of characters made from one nozzle willrequire l0 horizontal'sweeps. These can be made in saidoperativeembodiment in 50.14 milliseconds. Restated, each sweep requires 4.36milliseconds. Retrace time requires 0.654

milliseconds. i

In said embodiment a hydrostatic head of 0.718 inch of ink is maintainedas an operating condition. The inside diameter 7 of the bore of nozzlel8 is 0.0065 inch, its outside diameter being 0.010 inch, The diameterof aperture 39 is 0.030 inch and the accelerating electrode is spaced0.0435 inch from the downstream end of said nozzle.

Vertica electrodes 43 and 44 are spaced 0.045 inch (center to center)from the valving electrode 38; and horizonta electrodes 51 and 52 arespaced a like distance (center to center) from the vertica electrodes.Mask 50 is spaced 0.103 inch downstream from the horizontal" electrodes(center to center) and said mask is spaced 0.240 inch from platen 22.The thickness of each of the electrodes and of said mask is 0.0l0 inch,the valving electrode, the pair of vertical" electrodes and the pair ofhorizontal" electrodes each being disposed in a plane parallel to theplanes of the others and to the plane of mask 50.

Moreover, each electrode of each vertical" and horizontal pair thereofis spaced a distance from course 41 equal to the distance that the otherelectrode of such pair is spaced from said course. Furthermore, thespacing between the vertical" electrodes is 0.020 inch and the spacingbetween the horizontal" electrodes is 0.025 inch.

An ink which has been used effectively in the operative embodiment hasthe parameters of viscosity and resistivity which are set forth'in thecopending application of Robert .I. Dunlavey and Charles R. Winston,Ser. No. 853,825, filed Aug.

28, 1969, and assigned to the assignee of the present application. Anadequate jet printing stream which is controllable in the manner hereindescribed is drawn from nozzle 18 by an electrostatic field generated byimposing 3,S00 volts on nozzle l8 and l,000 volts on valving electrode38. By applying +l0,000 volts to platen 22, the ink stream, when in aprint mode, will have sufficient impetus to impinge on carrier 24 forprinting.

During operation of the apparatus the uppermost electrode 44 of thevertical pair thereof is maintained at reference or ground potentialwhen either a print or a nonprint mode prevails. To effect a print mode-450 volts is applied to the lower electrode 43 of said pair, This issufiicient under the conditions in the apparatus to deflect the inkstream along path 48 into mask 50, when the latter is maintained at+4,000 volts. During each voltage sweep, voltage on left electrode 51 isreduced from +l,600 volts to 0 while the voltage on the right electrode52 increases from 0 to +1,600 volts and will produce a single line ofthe raster.

The spacing between the upper edge 64 of the mask and path 41 is merely0.006 inch; the angles 0 and 7 (FIG. 2) are 235Vz minutes.

Under the conditions identified, printing can be effected which issquared" to carrier 24 while it is continuously driven at a velocity of1.944 inch per second.

As many modifications in the described construction and process could beconceived, and as many changes could be made therein without departingfrom the spirit and scope of the claims, it is intended that all mattercontained in the accompanying specification shall be considered asillustrative only and not in a limiting sense.

lclaim:

1. In an electrostatic printer for simultaneously printing a pluralityof two dimensional characters and being of the type adapted to generateone dimension of each two dimensional character by movement in astraight path of a carrier toward which inkdrops in a stream aredirected over a course from LII across a span relative ink applyingmeans and the other dimension of each character is generated byapplication of changing voltages across a pair of parallel firstelectrodes disposed in said span at an angle other than parallel to saidcourse and spaced apart transversely thereof for deflecting said streamin a succession of sweeps transversely of said straight path and at anangle other than perpendicular to the direction of said straight path,the improvement characterized by:

an array of horizontally aligned nozzles, each of said nozzlesassociated with a pair of parallel first electrodes forsimultaneouslyproviding a plurality of streams of ink;

a mask construction disposed downstream of said nozzles and defined by asawtooth edge configuration with a plurality of segments extendinglongitudinally of nozzle alignment, said configuration comprised ofedges respectively associated with said nozzles, each edge extendingparallel to the sweeps of the stream of ink from an associated nozzle,and

a pair of parallel second electrodes associated with each nozzle forproviding character definition by stream deflection, each pair of secondparallel electrodes spaced transversely of the spacing of associatedfirst electrodes and extending transversely of though at an angle otherthan perpendicular to an associated straight path, each pair of saidsecond electrodes having a first condition in which an associated streamimpinges said carrier during any portion of a sweep and a secondcondition in which such stream is prevented by said mask constructionfrom reaching said carrier during any portion of its sweep.

2. A combination according to claim 1 wherein said mask construction hasa window opening limited by said configuration.

3. A combination according to claim 2 wherein said sawtoothconfiguration has a plurality of slopes each thereof parallel to theothers and to the path of the sweeps of an associated nozzle.

i I? 8 b

1. In an electrostatic printer for simultaneously printing a pluralityof two dimensional characters and being of the type adapted to generateone dimension of each two dimensional character by movement in astraight path of a carrier toward which ink drops in a stream aredirected over a course from across a span relative ink applying meansand the other dimension of each character is generated by application ofchanging voltages across a pair of parallel first electrodes disposed insaid span at an angle other than parallel to said course and spacedapart transversely thereof for deflecting said stream in a succession ofsweeps transversely of said straight path and at an angle other thanperpendicular to the direction of said straight path, the improvementcharacterized by: an array of horizontally aligned nozzles, each of saidnozzles associated with a pair of parallel first electrodes forsimultaneously providing a plurality of streams of ink; a maskconstruction disposed downstream of said nozzles and defined by asawtooth edge configuration with a plurality of segments extendinglongitudinally of nozzle alignment, said configuration comprised ofedges respectively associated with said nozzles, each edge extendingparallel to the sweeps of the stream of ink from an associated nozzle,and a pair of parallel second electrodes associated with each nozzle forproviding character definition by stream deflection, each pair of secondparallel electrodes spaced transversely of the spacing of associatedfirst electrodes and extending transversely of though at an angle otherthan perpendicular to an associated straight path, each pair of saidsecond electrodes having a first condition in which an associated streamimpinges said carrier during any portion of a sweep and a secondcondition in which such stream is prevented by said mask constructionfrom reaching said carrier during any portion of its sweep.
 2. Acombination according to claim 1 wherein said mask construction has awindow opening limited by said configuration.
 3. A combination accordingto claim 2 wherein said sawtooth configuration has a plurality of slopeseach thereof parallel to the others and to the path of the sweeps of anassociated nozzle.